This sleeping bag has been designed with the coldest regions of Earth in mind. This is the warmest product of this kind in the world currently, as confirmed by a study performed by an independent laboratory. The sleeping bag is the 4th iteration of Radical H16, with the greatest number of modifications, which were the result of suggestions provided as part of long-term tests in Mongolia, Greenland, and Norway, at the South Pole, and on Cerro Torre. Based on the collected feedback, the designers decided to use a special waterproof fabric in the areas which are particularly prone to getting wet. Other changes include the use of an easily loosened face opening, a passive transmitter, and the best-quality down available on the market.